The following description relates primarily to the monitoring of estrus and ovulation and the planning of a useful fertilization time zone and a preferred fertilization time zone in sows but can be applicable to other animals.
Nowadays is known the strict relation that exists between the estrus and ovulation status, and the following features of the animal: blood temperature, vulva appearance and state of stress in presence of the boar.
On the basis of this relation, a typical method for the determination of the estrus and ovulation status of the sow consists in the evaluation by an expert staff, through direct observation of the animals, of at least one of the characteristics mentioned above.
In U.S. Pat. No. (Rodrian) 4,455,610 Jun. 19, 1984 is disclosed a tag carrying a mercury switch which can be attached to the animal to detect movement. Information relating to the amount of movement is used in a complicated system that detects estrus of the animal by comparing rates of movement.
In Published European Patent Application EP 1 200 119 A2 (Theelen) published Sep. 4, 2003 which corresponds to U.S. Published Application 2003/0069515 (now abandoned) is disclosed a complicated system that detects estrus of the sow by detecting standing movements by a sensor above the animal in response to stimulation by a boar or a simulated boar. Different steps of the estrus are detected by different responses to stimulation.
In UK Patent Application 2 076 259 (Rodrian) published Nov. 25, 1981 is disclosed a similar arrangement which is primarily concerned with a transceiver unit for receiving information from the transponder on the animal.
NL Patent Application 1012872 published Feb. 23, 2001 discloses a device for measuring animal lying time for detection of estrus In order to improve the effectiveness of fertilization it is necessary to detect the estrus properly, because the useful interval for the sow fertilization starts from the peak of heat. Thus it is necessary to detect when the heat starts and when the heat reaches a peak, otherwise the fertilization may fail. This requires conventionally the necessity for frequent inspections of the animals.
The technician also knows the fact that the fertilization has more probability to be effective if performed in a particular period of the estrus, so an inadequate survey of the estrus of a sow has as an effect and high probability of failure of fertilization, with a severe reduction for the sow productivity, which enters on estrus every 21 days.
Any failures thus significantly increase costs, of maintaining and feeding the animal during the time when it is non-productive. Also any repeated fertilization attempts to safeguard against failures significantly increase costs of semen and labor.
The conventional methods present some difficulties, for example the requirement for qualified staff dedicated to frequent inspections of every sow, and even in this situation fertilization is subject to the variability and possibility to failure which arises from the strong dependence upon the “human factor”.